Storm grates, or water drainage grates, are commonly located along paved roadways to transport surface water into underground storm drains, or to house utilities. Such grates are commonly constructed out of cast iron, and typically include parallel spaced bars in a grid pattern, with the openings between the bars suited for receiving surface water. The upper surface of the grate is typically level with the road surface (i.e. the pavement).
Storm grates are usually mounted on an associated frame which is embedded in the ground or in concrete pavement near the curb. An interior ledge or supporting shoulder of the associated frame supports the weight of the grate, which fits flush with the frame aperture, such that the grate can be readily removed if it becomes necessary to clean out the storm drain, or for some other purpose. Although storm grates can be very heavy, weighing up to one-hundred fifty pounds, they are quite often removed from their mounting frames by unauthorized persons as an act of theft or vandalism. The large opening left behind in the pavement represents a serious injury hazard to a person or a vehicle, and the stolen grates must be replaced, with consequent expense to the city.
Although lockable grate systems are known, standard heavy storm grates which are lowered into their mounting frames and thereafter not locked or secured in any manner are still commonly used in many municipalities. Therefore, there is a need to secure storm grates in place to prevent unauthorized removal and the subsequent hazards resulting from a stolen or unseated grate.
The prior art discloses various ways of securing storm grates. U.S. Pat. No. 7,201,533 to DeGreef discloses a locking mechanism for preventing removal of the grate from its mounting frame by unauthorized persons. The locking mechanism includes a grate hold-down device which overlaps and completely encircles one of the grate bars, a threaded nut attached to the mounting frame below the hold-down device, and a bolt extending downwardly through the hold-down device into threaded engagement with the nut.
U.S. Pat. No. 6,942,419 to Knak discloses a system grate assembly which includes a frame and a complimentary grate which is designed to be locked to the frame by a specific locking device which is located below the grate, and is inaccessible from the street level.
U.S. Pat. No. 5,340,232 to Spiess discloses a manhole cover interlocked with a complimentary mounting frame. The cover and frame are designed to function together, and include a securing device which allows the grating or cover to be fitted and removed easily. The securing device is not locked to the frame, and comprises a “spring-clip” type device rather than a lock.
U.S. Pat. No. 4,142,329 to Williams discloses a locking assembly for a grate having two subassemblies that can be added to existing installed storm grates to prevent loss of the grate through theft or vandalism. The first subassembly is secured to the grate by a pair of cross plates and a bolt. The second subassembly supports a horizontal movable locking member and a compression coil spring which keeps the locking member engaged with the grate frame. A removable pivotal lever is used to move the locking member against the force of the coiled spring, thereby permitting the grate to be removed by authorized personnel.
While such prior art grate locking devices and systems may be useful for their intended purposes, there remains a need for a storm grate security lock that can be fitted easily onto existing unsecured storm grates to prevent their theft and protect them from vandalism. It would therefore be advantageous to provide a locking device for an unsecured storm grate that can be installed without having to remove the storm grate, which provides strong locking capacity, and which utilizes an uncomplicated design that is easy to manufacture.